Numerically controlled machine tools are widely used today for machining works. Typically, a numerically controlled (NC) machine tool includes a wide variety of tools to allow precise machining by automatically controlling an operation of the machining tools and are primarily used for cutting, shaping, milling, turning, boring, drilling, grinding, or polishing of solid parts, such as metals. An example of basic configuration of an NC machine tool is shown a schematic diagram of FIG. 1.
As shown in FIG. 1, a typical NC machine tool 20 comprises a bed 12, with a table 6 which is carried on the bed 12 to be horizontally (X and X directions) and vertically (Z direction) movable on the bed 12. A work (not shown) to be machined is placed on the table 6 through a fixing means. A tool attachment mechanism (spindle) 8 is positioned over the table 6 for mounting a toolholder that holds a tool appropriate to a current process of machining. A control box 5 includes input means 4 such as a keyboard and a monitor 2 such as a CRT or an LCD display panel. The input means 4 functions as a man-machine interface and allows a user to input instructions and parameters to the NC machine tool 20. The monitor 2 displays the user's input data, current operation, various parameters for machining the work, etc.
An automatic tool exchanging device 10 is provided for automatically changing the tools appropriate for the types of machining process for the tool attachment mechanism 8. The automatic tool exchanging device 10 generally stores a plurality of tools from which it selects a suitable tool for the current job. The tools in the automatic tool exchanging device 10 are attached to the corresponding toolholders so that the selected tool is attached to the tool attachment mechanism 8 by the tool exchanging device 10.
Generally, toolholders to be used for NC machine tools are standardized in outer size and shape at the part which engages with the tool attachment mechanism. Thus, the tools can fit to an automatic tool exchanging device as well as to a tool attachment mechanism regardless of manufacturers or models of NC machine tools. The toolholders for NC machine tools for holding various tools are readily available in the market. One example of such a toolholder is illustrated in a front view of FIG. 2A.
A toolholder 30 shown in FIG. 2A is comprised of a tool holding portion 34 and an attachment portion 32. The attachment portion 32 has a hook 36 that will be inserted in the tool attachment mechanism 8. The attachment portion 32 is standardized so that the toolholder 30 can be used any standard NC machine tools. The tool holding portion 34 holds a tool (not shown), and the attachment portion 32 is fixed to the tool attachment mechanism 8 of the NC machine tool 20. The tool holding portion 34 is able to hold tools of different sizes and shapes.
As noted above, the outer shape and size of the attachment portion 32 is standardized to allow the toolholder 30 to be attached to the tool attachment mechanism 8 regardless of the manufacturer or type of the particular NC machine tools. Thus, as long as the toolholder 30 has the standardized shape and size of the attachment portion 32 as shown in FIG. 2A, the toolholder 30 can be used by different NC machine tools. When a tool is mounted on the tool attachment mechanism 8 through the toolholder 30, the NC machine tool knows the size and shape of the tool because of the machining program and controls the movement of the tool attachment mechanism (spindle) 8 and the table 6 incorporating the size and shape of the tool.
The toolholders 30 for NC machine tools described above have drawbacks in that they are generally expensive and can be financially burdensome especially for individual machinists to purchase many toolholders. Moreover, a user must have several different types of toolholders to accommodate various tools used for a project because inner structures of the toolholders are frequently different for accommodate different types of tools. It can be financially burdensome to purchase a new toolholder that is needed for a tool used only for a special project. Even when a machinist has a particular toolholder required for a project, a multiplicity of the same type of such toolholders may be necessary to complete the particular project.
Many machinists and machine houses generally have various collets that can attach to machine tools other than an NC machine tool. A collet is a type of toolholder for holding tools for traditional machine tool such as a lathe, milling machine, etc. An example of a collet is shown in a front view of FIG. 2B. Advantages of collets are that collets are relatively less expensive than toolholders used for NC machine tools and collets are readily available in the market. Moreover, because collets are common and traditionally used devices, machinists and machine houses are more likely to have a stock of them.
Accordingly, there is a need to combine the advantages of a collet used for traditional machining tools and a toolholder used for an NC machine tool, thereby allowing a desired tool to be used by an NC machine tool through a traditional collet without a NC machine toolholder for the particular tool.